U.S. patent application number 12/106529 was filed with the patent office on 2008-12-18 for roller conveyor and conveyance control method.
This patent application is currently assigned to FUJITSU LIMITED. Invention is credited to Tadashi Inoue.
Application Number | 20080308389 12/106529 |
Document ID | / |
Family ID | 40131293 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080308389 |
Kind Code |
A1 |
Inoue; Tadashi |
December 18, 2008 |
ROLLER CONVEYOR AND CONVEYANCE CONTROL METHOD
Abstract
A roller conveyor is disclosed that constitutes a conveying path
with plural rollers arranged in parallel. The roller conveyor
includes the plural rollers in alignment with one another on both
sides of the conveying path, and a roller driving motor provided to
each of the rollers. In the roller conveyor, the rollers are
directly linked to rotary shafts of the corresponding roller
driving motors.
Inventors: |
Inoue; Tadashi; (Kawasaki,
JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
FUJITSU LIMITED
Kawasaki-shi
JP
|
Family ID: |
40131293 |
Appl. No.: |
12/106529 |
Filed: |
April 21, 2008 |
Current U.S.
Class: |
198/617 ;
198/788 |
Current CPC
Class: |
B65G 47/261 20130101;
B65G 43/10 20130101; B65G 13/06 20130101 |
Class at
Publication: |
198/617 ;
198/788 |
International
Class: |
B65G 43/00 20060101
B65G043/00; B65G 13/06 20060101 B65G013/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2007 |
JP |
2007-156431 |
Claims
1. A roller conveyor constituting a conveying path with plural
rollers arranged in parallel, the roller conveyor comprising: the
plural rollers in alignment with one another on both sides of the
conveying path; and a roller driving motor provided to each of the
rollers, wherein the rollers are directly linked to rotary shafts
of the corresponding roller driving motors.
2. The roller conveyor according to claim 1, wherein side-wall
plates are provided on both sides of the conveying path so as to
hold the conveying path between them, each of the roller driving
motors is attached outside the corresponding side-wall plate, each
of the rollers is arranged on a conveying path side of the
corresponding side-wall plate, and each of the rotary shafts of the
roller driving motors is connected to the corresponding roller
through the corresponding side-wall plate.
3. The roller conveyor according to claim 1, further comprising: a
control part that separately controls a rotational speed of each of
the roller driving motors.
4. The roller conveyor according to claim 3, wherein the roller
driving motors are induction motors, and the control part performs
frequency control of current to be supplied to the induction
motors.
5. The roller conveyor according to claim 3, wherein the roller
driving motors are pulse motors, and the control part performs
pulse control of current to be supplied to the pulse motors.
6. A conveyance control method for controlling a conveyance of
plural conveyed objects in a conveying path formed by connecting
plural roller conveyor units to each other, each roller conveyor
unit being composed of the roller conveyor according to claim 3,
wherein one of the plural conveyed objects on the conveying path is
stopped at a first roller conveyor unit among the plural roller
conveyor units, while another conveyed object on a second roller
conveyor unit among the plural roller conveyor units is conveyed
across the first roller conveyor unit.
7. The conveyance control method according to claim 6, wherein some
of the rollers of the first roller conveyor unit are driven to
rotate in synchronization with the rollers of the second roller
conveyor unit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to roller conveyors
and, more specifically, to a roller conveyor that drives each of
plural rollers to convey a conveyed object.
[0003] 2. Description of the Related Art
[0004] Roller conveyors constituting a conveying path with plural
rollers continuously arranged in parallel are called free-flow
conveyors, and they are often used, for example, to convey palettes
having a manufactured object mounted thereon in manufacturing
facilities.
[0005] Such a roller conveyor is provided with a driving force
transmission mechanism for transmitting the driving force of a
motor to each roller. Examples of the driving force transmission
mechanism include a mechanism using a train of gears, a mechanism
using pulleys and a belt, a mechanism using a timing belt or a
chain, etc.
[0006] When the roller conveyor provided with the above driving
force transmission mechanism is used, for example, in a clean room,
dust (minute powder particles) generated by the driving force
transmission mechanism may pollute the clean environment inside the
clean room. In other words, when the train of gears is used as the
driving force transmission mechanism, abrasion powder generated at
a part where the gears are meshed with each other may be scattered
to surroundings. Moreover, when the pulleys and the belt are used
as the driving force transmission mechanism, abrasion powder
resulting from the sliding of the belt on the pulleys may be
scattered to the surroundings.
[0007] In order to prevent such a scattering problem of abrasion
powder, a method has been disclosed in which the driving force
transmission mechanism is arranged in a space isolated from the
clean environment so as to exhaust and remove minute powder
particles generated by the driving force transmission mechanism.
Furthermore, another method has been disclosed in which water is
dropped onto the driving force transmission mechanism to wash out
minute powder particles so as not to be scattered in the air.
[0008] However, the above methods require large-scale installations
such as providing an isolated space and an exhaust unit or water
supplying and collecting units, causing a great deal of
inconvenience to users who use the roller conveyor in the clean
room with a limited space.
[0009] Accordingly, a roller conveyor has been proposed that has a
mechanism for directly linking motors with plural rollers and
synchronizing the rotations of the plural motors to rotate the
rollers (see, for example, Patent Document 1). In this case,
because the rollers are directly driven by the corresponding
motors, the driving force transmission mechanism is not required.
As a result, the scattering of minute powder particles due to the
abrasion of components of the driving force transmission mechanism
does not occur.
[0010] Patent Document 1: JP-A-2004-131222
SUMMARY OF THE INVENTION
[0011] The roller conveyor of Patent Document 1 can provide a
configuration without the driving force transmission mechanism, but
both ends of the rollers are supported by bearings. Therefore,
abrasion powder may be generated by the bearings.
[0012] Furthermore, in order to stop a conveyed object midway
through a conveying path, the provision of stoppers along the
conveying path is required. The stopper serves as a mechanism for
hitting, for example, against a pallet having a conveyed object
mounted thereon to forcibly stop the same. However, the provision
of many stoppers along the conveying path causes an increased cost
of the roller conveyor.
[0013] In addition, although the roller conveyor can stably convey
a conveyed object at a constant speed because it synchronizes the
plural rollers to rotate at a constant speed, it cannot change the
conveying speed of the conveyed object midway through the conveying
path. For example, if cycle time is different for each
manufacturing process in a case where a manufactured object is
conveyed between the processes, it is preferable that the conveying
speed between the processes be variable. However, the roller
conveyor does not have such control over the conveying speed.
[0014] The present invention has been made in view of the above
problems and may provide a roller conveyor that reduces the
scattering of dust due to the driving of rollers.
[0015] Also, the present invention may provide a roller conveyor
capable of partially controlling a conveying speed midway through a
conveying path and a conveyance control method using the roller
conveyor.
[0016] In order to attain the above object, according to one aspect
of the present invention, there is provided a roller conveyor
constituting a conveying path with plural rollers arranged in
parallel. The roller conveyor comprises the plural rollers in
alignment with one another on both sides of the conveying path; and
a roller driving motor provided to each of the rollers, wherein the
rollers are directly linked with rotary shafts of the corresponding
roller driving motors.
[0017] Also, according to another aspect of the present invention,
there is provided a conveyance control method for controlling the
conveyance of plural conveyed objects in a conveying path formed by
connecting plural roller conveyor units to each other, each roller
conveyor unit being composed of the above roller conveyors, wherein
one of the plural conveyed objects on the conveying path is stopped
at a first roller conveyor unit among the plural roller conveyor
units, while another conveyed object on a second roller conveyor
unit among the plural roller conveyor units is conveyed across the
first roller conveyor unit.
[0018] According to an embodiment of the present invention, a
roller driving motor is provided to each of the plural rollers, and
the rotary shafts of the roller driving motors are directly linked
with the corresponding rollers. Therefore, the rollers are
supported and rotated by the roller driving motors. Accordingly, a
driving force transmission mechanism for transmitting a driving
force to the rollers and bearings for rotatably supporting the
rollers are not required. As a result, the scattering of minute
powder such as abrasion powder generated by a driving force
transmission mechanism and the bearings does not occur, thereby
making it possible to maintain a clean environment around the
roller conveyor.
[0019] In addition, because the driving of the rollers can be
separately controlled, the conveyance of a conveyed object can be
separately controlled midway through the conveying path, thereby
making it possible to efficiently convey plural conveyed objects
and reduce the entire conveying time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Other objects, features and advantages of the present
invention will become more apparent from the following detailed
description when read in conjunction with the accompanying
drawings, in which:
[0021] FIG. 1 is a perspective view of a roller conveyor according
to an embodiment of the present invention;
[0022] FIG. 2 is a simplified cut-open view of a part of a
side-wall plate to which a roller driving motor is attached;
[0023] FIGS. 3A and 3B are diagrams showing examples of a
conveyance control method for pallets in a case where roller
conveyor units are connected to one another to form a conveying
path; and
[0024] FIG. 4 is a flowchart for explaining the conveyance control
method shown in FIG. 3A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] Referring to the accompanying drawings, a description is
made of a roller conveyor according to an embodiment of the present
invention. FIG. 1 is a perspective view of the roller conveyor
according to the embodiment. The roller conveyor shown in FIG. 1 is
a so-called free-flow conveyor and configured such that plural
rollers are rotated to convey a pallet 2 while the pallet 2 is
supported by the rollers. A conveyed object is mounted on the
pallet 2 and conveyed together with the pallet 2.
[0026] The roller conveyor shown in FIG. 1 is configured as a
roller conveyor unit 4 in which six pairs of the rollers 10 are
arranged one roller of each of the pairs on each side of a
conveying path. In manufacturing lines, etc., plural of the roller
conveyor units 4 are arranged side by side along the conveying path
to form a long conveying path.
[0027] The roller conveyor unit 4 has side-wall plates 8 that are
arranged in parallel at a predetermined interval while standing on
a substrate 6. The conveying path is formed between the side-wall
plates 8. The rollers 10 are in alignment with one another inside,
or on the conveying path side of, the left and right side-wall
plates 8. In an example shown in FIG. 1, six rollers 10 are
arranged inside one side-wall plate 8 and another six rollers 10
are arranged inside the other side-wall plate 8 at facing
positions.
[0028] Each of the rollers 10 is not a long roller extending over
the entire width of the conveying path, but it has a length only to
support the ends of the pallet 2. In other words, the pallet 2 is
conveyed with its left and right ends supported by the rollers 10
in a conveying direction.
[0029] On the sides of the side-wall plates opposite from the
rollers 10, roller driving motors 12 are arranged. FIG. 2 is a
simplified cut-open view of a part of the side-wall plate 8 to
which the roller driving motor 12 is attached. The motor main body
12a of the roller driving motor 12 is fixed to the side-wall plate
8 by screws, etc. The rotary shaft 12b of the roller driving motor
12 is arranged to extend in a through-hole 8a of the side-wall
plate 8.
[0030] The roller 10 has a cylindrical attachment part 10a that is
to be inserted in the through-hole 8a of the side-wall plate 8. A
hole is formed in the attachment part 10a, and the rotary shaft 12b
of the roller driving motor 12 extending in the through-hole 8a
fits in the hole. The rotary shaft 12b is inserted in the hole and
fixed by a screw 14. Each of the left and right side-wall plates 8
has six roller driving motors 12 attached, and the six rollers 10
are attached to the rotary shafts 12b of the corresponding roller
driving motors 12.
[0031] The motor main body 12a of the roller driving motor 12 has a
motor and a reduction mechanism, and the rotary shaft 12b is
rotated at a rotational speed reduced by the reduction mechanism.
As the motor 12, a synchronous motor such as an induction motor
capable of being frequency controlled regarding the number of
rotations or a pulse motor is available. The roller driving motor
12 is electrically connected to a controller 16 and driven by
current supplied from the controller 16. The controller 16 is
configured to separately control the driving or rotational speed of
each of the roller driving motors 12.
[0032] When the induction motor is used as the roller driving motor
12, the controller 16 has a frequency control power unit. The
frequency control power unit separately controls the frequency of
current to be supplied to the twelve roller driving motors 12.
Accordingly, the controller 16 can separately control the
rotational speeds of the twelve rollers 10. In general, because the
corresponding rollers 10 on left and right sides may be rotated at
the same speed, it is only required to supply current having the
same frequency to a pair of the left and right roller driving
motors 12.
[0033] Moreover, when a pulse motor is used as the roller driving
motor 12, the controller 16 has a pulse control power unit. The
pulse control power unit separately controls pulse currents to be
supplied to the twelve roller driving motors 12. Accordingly, the
controller 16 can separately control the rotational speeds of the
twelve rollers 10. In general, because the corresponding rollers 10
on left and right sides may be rotated at the same speed, it is
only required to supply the same pulse current to a pair of the
left and right roller driving motors 12.
[0034] According to the roller conveyor having the above
configuration, one roller driving motor 12 is provided to one
roller 10, and the roller 10 is directly linked to the rotary shaft
12b of the roller driving motor 12. Therefore, a driving force
transmission mechanism is not required. As a result, the scattering
of dust such as minute powder particles due to the abrasion of
components of a driving force transmission mechanism does not
occur. Furthermore, because the roller 10 is supported and rotated
by the rotary shaft 12b of the roller driving motor 12, a bearing
for rotatably supporting the roller 10 need not be provided. As a
result, the scattering of dust such as minute powder particles due
to the abrasion of components of the bearing does not occur.
[0035] As described above, the roller conveyor unit 4 according to
the embodiment does not cause the scattering of dust such as minute
powder particles to the surroundings. Therefore, it is suitable for
conveying a conveyed object while maintaining a clean environment
such as a clean room.
[0036] According to the roller conveyor unit 4 of the embodiment,
the conveying path is formed between the left and right side-wall
plates 8 and the pallet 2 is conveyed therebetween. Here, the
rollers 10 do not extend over the entire width of the conveying
path. Therefore, a large gap is present between the left and right
rollers 10 to thereby form a large space. By using this space, it
is possible to arrange, for example, a stopper mechanism for
stopping the pallet 2 and a positioning unit that positions the
pallet 2 at a stop position, thereby enhancing the degree of
freedom for arranging peripheral devices with respect to the
conveying path.
[0037] Next, a description is made of a conveyance control method
when the roller conveyor unit 4 according to the embodiment is
used.
[0038] FIGS. 3A and 3B are diagrams showing examples of the
conveyance control method for pallets in a case where the roller
conveyor units are connected to one another to form the conveying
path. FIG. 3A is a diagram showing the conveyance control method in
a case where all the rollers of one roller conveyor unit are
synchronized to be driven to rotate. FIG. 3B is a diagram showing
the conveyance control method that can be performed by the roller
conveyor unit according to the embodiment.
[0039] In an example shown in FIG. 3A, six rollers are provided to
each of three roller conveyor units 20A, 20B, and 20C provided in
series, and they are driven by one motor via a belt. Accordingly,
all the rollers of one roller conveyor unit are synchronized to
rotate at the same speed. In this case, in order to smoothly convey
pallets from one roller conveyor unit to the next roller conveyor
unit, all the conveying speeds of the roller conveyor units must be
the same. Accordingly, all the moving speeds and the moving
distances of the pallets on the roller conveyor units must be the
same.
[0040] For example, when the pallet on the rightmost roller
conveyor unit 20A is conveyed to the central roller conveyor unit
20B (moving distance: 300 mm), the pallet on the central roller
conveyor unit 20B is also conveyed 30 mm to the leftmost roller
conveyor unit 20C. In other words, all the rollers of the three
roller conveyor units 20A, 20B, and 20C are caused to
simultaneously start their driving at the same speed. The three
pallets on the three roller conveyor units 20A, 20B, and 20C are
conveyed the same distance at the same speed, and all the rollers
of the three roller conveyor units 20A, 20B, and 20C are caused to
simultaneously stop their driving.
[0041] In the case of the example shown in FIG. 3A, assume that
processing, for example, assembling of a workpiece on the pallet,
is performed with respect to conveyed objects on the pallets at
predetermined positions of the roller conveyor units 20A, 20B, and
20C. Also, assume that processing time at the roller conveyor unit
20B is longer than the processing time at the roller conveyor unit
20A. In this case, even if the processing at the roller conveyor
unit 20A is completed first, the pallets cannot be conveyed until
the processing at the roller conveyor unit 20B is completed. In
other words, the pallets on the roller conveyor units 20A, 20B, and
20C must be simultaneously conveyed after the processing at the
roller conveyor unit 20B is completed. Furthermore, because the
moving distances of the pallets are 300 mm, conveying time
corresponding to 300 mm is required.
[0042] Next, a description is made of the conveyance control method
that can be performed by the roller conveyor units 4A, 4B, and 4C
according to the embodiment as shown in FIG. 3B. Note that a
flowchart for the conveyance control method shown in FIG. 4 is also
referred to, besides FIG. 3B.
[0043] According to the roller conveyor units 4A, 4B, and 4C of the
embodiment, the rotational speeds of the rollers 10 can be
separately controlled. Here, similarly to the example shown in FIG.
3A, assume that processing such as assembling a workpiece is
performed with respect to conveyed objects on the pallets at
predetermined positions of the roller conveyor units 4A, 4B, and 4C
and processing time at the roller conveyor unit 4B is longer than
processing time at the roller conveyor unit 4A. In this case,
unlike the example shown in FIG. 3A, when the processing is first
completed with respect to the pallet on the roller conveyor unit 4A
(Yes in step S1), it is possible to immediately start conveying the
pallet 100 mm in advance (step S2). In other words, only a group
10A of the rollers 10 shown in FIG. 3B is driven to convey only the
pallet on the roller conveyor unit 4A 100 mm. The group 10A of the
rollers 10 includes the rollers 10 of the roller conveyor unit 4A
and one roller 10 of the roller conveyor unit 4B. By driving these
rollers simultaneously, it is possible to convey a tip end of the
pallet on the roller conveyor unit 4A to the roller conveyor unit
4B.
[0044] When only the pallet on the roller conveyor unit 4A is
conveyed 100 mm (Yes in step S3), the driving of the group 10A of
the rollers 10 is stopped to stop conveying the pallet on the
roller conveyor unit 4A and these rollers are caused to wait for
the completion of the processing at the roller conveyor units 4B
and 4C. When the processing at the roller conveyor units 4B and 4C
is completed (Yes in step S4), all the rollers 10 of the roller
conveyor units 4A, 4B, and 4C are rotated in synchronization with
each other to convey the pallets on the roller conveyor units 4A,
4B, and 4C at the same speed (step S5).
[0045] Because the pallet on the roller conveyor unit 4A has
already been conveyed 100 mm, it will reach the predetermined
position on the roller conveyor unit 4B when conveyed an additional
200 mm after the driving of the rollers 10 is started (Yes in step
S6). In the example shown in FIG. 3A, the pallet on the roller
conveyor unit 20A is conveyed 300 mm to the position on the roller
conveyor unit 20B after the processing at the roller conveyor unit
20B is completed and then the rollers are driven. In the example
shown in FIG. 3B, on the other hand, the pallet on the roller
conveyor unit 4A is required to be conveyed only an additional 200
mm. In other words, if it is assumed that the pallet is conveyed at
the same speed, the pallet on the roller conveyor unit 4A can be
conveyed to the position on the roller conveyor unit 4B in
two-thirds the time required for conveying the pallet between the
roller conveyor units. Accordingly, the conveying time between
processes and the entire processing time can be reduced.
[0046] Even if the pallet on the roller conveyor unit 4A reaches
the position on the roller conveyor unit 4B (Yes in step S6) and
the processing at the roller conveyor unit 4B is started (step S7),
the conveyance of the pallet previously positioned on the roller
conveyor unit 4B is continued. Then, when the pallet on the roller
conveyor unit 4B is conveyed 300 mm and reaches the position on the
roller conveyor unit 4C (step S8), the driving of the rollers 10 of
the roller conveyor unit 4C is stopped and the processing at the
roller conveyor unit 4C is started (step S9).
[0047] As described above, the conveying path using the roller
conveyor unit according to the embodiment makes it possible to
convey a conveyed object regardless of another conveyed object on
the conveying path. Therefore, the conveyed object ready for
conveyance can be conveyed to an adequate position in advance,
thereby making it possible to reduce time required for a conveying
process. In other words, because the driving of the rollers can be
separately controlled, the conveyance of a conveyed object can be
separately controlled midway through the conveying path, thereby
making it possible to efficiently convey plural conveyed objects
and reduce the entire conveying time.
[0048] The present invention is not limited to the specifically
disclosed embodiment, and variations and modifications may be made
without departing from the scope of the present invention.
[0049] The present application is based on Japanese Priority Patent
Application No. 2007-156431, filed on Jun. 13, 2007, the entire
contents of which are hereby incorporated by reference.
* * * * *